Zein is a hydrophobic, alcohol soluble protein which comprises 50% or more of the endosperm protein of the maize seed. It is packaged in single membrane bound organelles called protein bodies. Zein messenger RNA is translated on the surface of the protein body membrane. The nascent chains are processed by: 1) cleavage of a signal peptide, and 2) glucosylation. These activities are presumed to be associated with the protein body membrane and occur before or during transport through the membrane. The zein protein bodies are easily isolated free of other cellular components. No other proteins are made on these membranes. It is proposed that zein protein bodies constitute a simplified and accessible means for identifying the components which specify that a particular protein is made on, processed, and transported through a membrane. Messenger RNAs that code for the two zein polypeptides have been purified free of all other RNA species. Their lengths have been determined. They are "capped" and have polyadenylate tails. Double stranded DNA reverse transcripts have been prepared using the messages as templates and inserted into a bacterial plasmid. Some of the resultant plasmid clones appear to contain nearly full length inserts of the zein mRNA sequences.